1. Field of the Invention
The field of this invention is generally that of adhesives useful for bonding solar film, and for providing solar films for adherence to glass or metal substrates.
2. Description of the Prior Art
Flexible polymeric substrates have been adhered to dissimilar substances, particularly glass, by a variety of adhesives. The need for adhering polymeric substrates to glass arises as one of a variety of concerted efforts in recent years to conserve energy. In hot weather, it is important to reduce the transmission of sunlight into a room while still maintaining adequate visibility.
Obviously, the less radiation which enters a room, the less need for energy expenditures for air-conditioning. One way in which this has been accomplished is by the use of reflective film, so-called "solar film", which is adhered directly onto window glass.
The common type of solar film comprises a base sheet of a transparent polyester, usually a polyethylene terephthalate film, onto one side of which a thin but reflective and transparent layer of aluminum has been vapor-deposited. It is of course possible to provide solar films with coatings of metals other than aluminum thereon. Onto the metal surface either a protective coating may be applied or a polymer film, usually polyester, dyed or clear, may be laminated with the use of a polymeric adhesive. Solar films are described in U.S. Pat. Nos. 4,157,417; 3,681,179; 4,095,013, and 3,152,950.
There is also another variety of solar film in use which does not have a metallic coating thereon, but which is dark in color and functions to exclude glare. This type is referred to in the trade as "dark smoke".
Thus, when a partially reflective solar film is in place, sunlight is partially reflected at the surface of the window with the result that there is a significant reduction in the amount of sunlight entering and thereby heating a room.
In addition, a protectively coated, opaquely metallized polyester film coated on its second surface with a polyester adhesive, as described in Example 12 hereinafter set forth, may be adhered to substrates other than glass, such as aluminum or steel, for example. The finished composite can function as a mirror to reflect light. If the finished composite is curved, e.g., parabolically, then sunlight can be focused to furnish a source of heat, for use in heating water, for example. The film can be considered disposable and when no longer useful, can be peeled from the substrate and replaced with new reflector film.
Various adhesives and adhesive systems have been described for adhering solar film to window glass. U.S. Pat. No. 3,290,203 (Antoneon and Berger) discloses water-activatable adhesives comprising casein, glue, polyvinyl alcohol and vinyl ether polymers.
U.S. Pat. No. 3,152,950 (Palmquist) discloses the use of a pressure-sensitive adhesive compound of a rubbery butadiene-acrylonitrile polymer and a phenol-formaldehyde resin.
U.S. Pat. No. 3,308,004 (Rouault) discloses translucent panels having a protective coating of reinforced cross-linked polyester resin.
U.S. Pat. No. 3,619,335 (Bryan) discloses laminates having a removable flexible polymeric film plasticized with a nonionic surfactant.
U.S. Pat. No. 3,681,179 (Theissen) discloses the use of a water soluble film-forming material which is deposited over a pressure-sensitive adhesive layer on the aluminum coated side of solar film. The water soluble film-forming material includes ethyl cellulose, or vinyl ether-maleic acid copolymer, or an ethylene oxide polymer.
U.S. Pat. No. 4,095,013 (Burger) teaches the use of a cling adhesive comprising a plasticized solvent-soluble copolymer consisting of vinyl chloride copolymerized with vinyl acetate, vinyl alcohol, or dibasic acid, or vinylidene chloride-acrylonitrile copolymer.
U.S. Pat. No. 4,146,585 (Ward) teaches a process for producing a silane grafted copolymer which comprises reacting a silane with vinyl chloride, hydroxyalkyl acrylate and a polymerizable monomer selected from the group consisting of alkyl esters of alpha, beta ethylenically unsaturated carboxylic acids and vinyl esters of saturated fatty acids.
U.S. Pat. No. 4,157,417 (Murphy) discloses an adhesive for a solar film wherein the adhesive comprises a physical mixture of an alkyl monoester of poly (methyl vinyl ether/maleic anhydride) and a silane such as beta-3,4(epoxycyclohexyl) ethyltrimethoxysilane or gamma-glycidoxypropyltrimethoxysilane with certain diols and aryl ethers.
U.S. Pat. No. 4,031,120 (Gervase) teaches the use of isocyanato organosilanes in combination with polyisocyanates and polymeric materials as adhesive materials for bonding vulcanizable elastomers at elevated temperatures to inorganic substrates.
Thus, there is a continuing need for an adhesive which can be applied directly to solar film for adherence to window glass or to metals, and which will provide early and long-term bond strength upon exposure to sunlight, heat and humidity.
It is therefore the principal object of this invention to provide adhesive compositions which can be applied directly to solar film for direct adherence to window glass or to metals, which adhesives exhibit good early bond strength and excellent bond strength upon long-term exposure to sunlight, heat and humidity.